优化目标C代码访问联系人

Question

我有一些代码可以从Addreesbook复制联系人。如果联系人数量较少，它可以完美运行。现在在我的手机中有1200个联系人，当我尝试复制它们时，应用程序崩溃了。任何人都可以帮助我优化此代码或重写代码吗？我使用的代码添加如下：

ABAddressBookRef addressBook = ABAddressBookCreate();
    CFArrayRef allPeople = ABAddressBookCopyArrayOfAllPeople(addressBook);
    CFIndex nPeople = ABAddressBookGetPersonCount(addressBook);
    NSString *requestContactsString = @"<contacts>";    

    for (int i=0; i<nPeople; i++)
    {
        NSLog(@"Started : %d", i);
        ABRecordRef ref = CFArrayGetValueAtIndex(allPeople, i);
        CFTypeRef firstName = ABRecordCopyValue(ref, kABPersonFirstNameProperty);
        CFTypeRef lastName = ABRecordCopyValue(ref, kABPersonLastNameProperty);
        CFTypeRef email = ABRecordCopyValue(ref, kABPersonEmailProperty);
        CFTypeRef phone = ABRecordCopyValue(ref, kABPersonPhoneProperty);
        requestContactsString = [requestContactsString stringByAppendingFormat:@"<item>"];
        if(firstName)
        {
            requestContactsString = [requestContactsString stringByAppendingFormat:@"<firstname>%@</firstname>", firstName];
            CFRelease(firstName);
            firstName = nil;
        }
        if(lastName)
        {
            requestContactsString = [requestContactsString stringByAppendingFormat:@"<lastname>%@</lastname>", lastName];
            CFRelease(lastName);
            lastName = nil;
        }
        if(email)
        {
            if(ABMultiValueGetCount(email)>0)
            {
                CFTypeRef em = ABMultiValueCopyValueAtIndex(email, 0);
                requestContactsString = [requestContactsString stringByAppendingFormat:@"<email>%@</email>", em];
                CFRelease(em);
            }
            CFRelease(email);
            email = nil;
        }
        if(phone)
        {
            if(ABMultiValueGetCount(phone)>0)
            {
                CFTypeRef ph = ABMultiValueCopyValueAtIndex(phone, 0);
                requestContactsString = [requestContactsString stringByAppendingFormat:@"<phone>%@</phone>", ph];
                CFRelease(ph);
            }
            CFRelease(phone);
            phone = nil;
        }
        requestContactsString = [requestContactsString stringByAppendingFormat:@"</item>"];
    }

    if(allPeople)
    {
        CFRelease(allPeople);
        allPeople = nil;
    }
    if(addressBook)
    {
        CFRelease(addressBook);
        addressBook = nil;
    }
    requestContactsString = [requestContactsString stringByAppendingFormat:@"</contacts>"];
    NSString *hashedContactsString = [self generateHashedPassword:requestContactsString];

Answer 1

我能看到的主要效率低下是使用[NSString stringByAppendingFormat]每次调用时都会创建一个新的NSString对象。 这意味着您有大量的长自动释放NSString对象，这些对象在下一次运行循环之前不再使用（除非您使用的是 ARC，在这种情况下，情况可能会更好）。

我认为您可以通过requestContactsString成为NSMutableString并使用[NSMutableString appendString]（参考）来更好地利用内存并获得更好的性能。 这将修改现有对象，分配更多内存来接受新字符串。

每个追加将如下所示：

[requestContactsString appendString:[NSString stringWithFormat:@"<lastname>%@</lastname>", lastName]];

这仍然会创建大量自动释放的对象，但它们要小得多。

Answer 2

使用NSMutableString并使用appendFormat:方法生成 XML。在你的循环中，你正在多次复制你到目前为止组装的整个字符串。